The print command, by itself, sends the current graphics figure to the printer. See help printopt about setting default options in an M-file.
MATLAB will print in portrait orientation (vertical longest, in the middle of the page, 4/3 aspect ratio) unless you specify otherwise with orient prior to printing. orient landscape changes to landscape (horizontal longest), portrait to the default, and tall to full-page portrait; with no argument, orient returns the current orientation.
To save the picture, print filename will save the current graphics figure; if filename does not have an appropriate suffix (e.g. .ps, .eps, .jet), the default mode will be used and the default suffix added. Specify -append to append to an existing file instead of overwriting it (the default). To save a non-current figure, specify -fnumber; to save in a specific format, specify -ddevice. See help print.